a)
\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{47}\\{35}\end{array}}\\\hline{\,\,\,\,82}\end{array}\) \(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{82}\\{47}\end{array}}\\\hline{\,\,\,35}\end{array}\)
\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{526}\\{147}\end{array}}\\\hline{\,\,\,\,673}\end{array}\) \(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{673}\\{147}\end{array}}\\\hline{\,\,\,526}\end{array}\)
b) 350 + 42 – 105 = 392 – 105 = 287
1 000 – 300 + 77 = 700 + 77 = 777.